Chapter 3

The Cell (part 1)

The Cell Theory

• Three Principles

1. All organisms are composed of cells

2. Cells are the smallest living units of life

3. All cells arise from pre-existing cells (by

cell division)

Cells Are Highly Structured

Eukaryotic (“with nucleus”) cells are highly “compartmentalized”

plasma membrane

nucleus: information center

cytoplasm: fluid within membrane

organelles: structures with specialized functions

Prokaryotes have no nucleus or true organelles

Prokaryotes have no nucleus or true organelles

The Plasma Membrane

• Structure of the plasma membrane

Structural Features of the Plasma

Membrane

• Lipid bilayer

– Phospholipids: polar head and nonpolar tail

– Cholesterol: makes membrane a bit more

rigid

– Proteins: provide means of transportation

through membrane

– Carbohydrates: provide recognition for cells

and organisms

Movement Across the Plasma

Membrane

• Diffusion

– Movement from area of high

concentration to low

• Passive transport: no energy required

Facilitated Diffusion

• Diffusion that uses transport (carrier)

proteins in membrane to assist moving

molecules across the membrane both:

– Down the concentration gradient

– Without expending energy

Active Transport

• Active transport uses proteins and

energy to move substances from an

area of lower concentration to an area

of higher concentration

Active Transport Proteins Use Energy

Osmosis

• Osmosis: net diffusion of water across

a semi-permeable membrane

Osmosis and Tonicity

Endocytosis (Phagocytosis)

Moves Materials in Bulk

• Endocytosis moves material into cell

• Example: WBC engulfs bacteria

Exocytosis Moves Materials in

Bulk

• Exocytosis moves material out of the

cell

• Example: secretion of hormones

Structure and Function of the Nucleus

• Functions:

– Contains the genetic information of the cell

– Controls the function & the operations of the cell

• Structural features:

– Double-layered nuclear membrane

– Nuclear pores

– Chromosomes/chromatin

– Nucleolus (synthesizes ribosomes)

Our Cells Are Highly Structured

• Chromosomes contained in the

nucleus are made of DNA

Endoplasmic Reticulum (ER)

Endoplasmic Reticulum (ER) and Ribosomes

• Ribosomes: used in synthesis of proteins

– Free and membrane bound

• Endoplasmic Reticulum (ER): packages the

proteins

– Smooth ER: no ribosomes, lipid synthesis &

detoxifies alcohol and drugs

– Rough ER: has ribosomes, protein synthesis